Project Summary Drug combination therapy has revolutionized cancer treatment and is now the mainstay of most modern regimens. In spite of the success, it is evident that in most cases, the cancer either does not respond to the initial treatment or a form of the cancer emerges that is cross-resistant to multiple drugs. Investigation into the molecular causes of cancer and dramatic improvements to the drug discovery process have created a new class of molecularly targeted agents that have proven to be effective in patients that are non-responsive or have become resistant to first- line chemotherapeutic cocktails. However in most indications, only a small minority of the patients respond to the drug and resistance emerges rapidly resulting in new therapies with limited clinical benefit. Although targeted therapies have significant limitations as single agents, their unique targets and limited side effect profiles present a growing opportunity for more effective treatments using combination therapies. It has been shown that targeted therapies can act synergistically by targeting the same pathway, a complementary pathway or alter signaling feedback loops that enhance signaling. Thus, in order to define novel combination therapies, it is necessary to define how the drugs interact with the cellular machinery through the definition of drug signatures. However, this is generally not possible with existing technologies. The goal of this Phase II SBIR is to create a system that can monitor more than 100 signaling events in 10 cell lines simultaneously for the high-throughput generation of drug signatures. Using this discovery tool it will be possible to explore drug synergy with the detail necessary to identify novel advantageous combinations.